Abstract
The bluefin tuna longline fishery is one of the most important pelagic fisheries in the Mediterranean but recently there has been increasing concern about the catches of non-target species. This study presents an assessment of the non-target by-catch from the Maltese bluefin tuna longline fleet and examines the effect of various environmental and spatio-temporal factors on non-target species catch rates. Field observations were made during 85 fishing days.
In terms of number, bluefin tuna comprised a relatively small portion of the total catch while the loggerhead turtle (Caretta caretta) was the predominant by-catch species. Catch Per Unit Effort (CPUE) was calculated in terms of weight (kg/1000hooks/hr) and number (no/1000hooks/hr) for all the species caught. Generalized Linear Mixed Models (GLMMs) were applied to examine the effect of environmental and spatio-temporal variables on non-target bycatch CPUE. The model for CPUE (number) was not found to be significant. Date, lunar cycle,
species and longitude were found to be significantly correlated with CPUE (weight). The results of this study suggests the need for the continual implementation of mitigation measures to minimise the impacts of fishing activities on threatened non-target species in the Mediterranean.
In terms of number, bluefin tuna comprised a relatively small portion of the total catch while the loggerhead turtle (Caretta caretta) was the predominant by-catch species. Catch Per Unit Effort (CPUE) was calculated in terms of weight (kg/1000hooks/hr) and number (no/1000hooks/hr) for all the species caught. Generalized Linear Mixed Models (GLMMs) were applied to examine the effect of environmental and spatio-temporal variables on non-target bycatch CPUE. The model for CPUE (number) was not found to be significant. Date, lunar cycle,
species and longitude were found to be significantly correlated with CPUE (weight). The results of this study suggests the need for the continual implementation of mitigation measures to minimise the impacts of fishing activities on threatened non-target species in the Mediterranean.
Original language | English |
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Article number | SCRS/2009/059 |
Pages (from-to) | 2262-2269 |
Number of pages | 8 |
Journal | Collective Volume of Scientific Papers |
Volume | 65 |
Issue number | 6 |
Publication status | Published - 2010 |
Keywords
- long lining
- tuna fisheries
- by-catch
- CPUE
- environmental factors